Magnetic fishing tool



J. H. KIRBYI 2,668,077

MAGNETIC FISHING TOOL Feb. 2, 1954 2 Shets-Sheet vl Filed July 30, 1952 uvmvrox.

wig g g" I A'TTORNE Y J. H. KIRBYIII MAGNETIC FISHING TOOL Feb. 2, 1954 2 Sheets-Sheet 2 FIIII'IWH/ zrllllffdaf l w 7 Filed July 30, 1952 A TTOR/VEV Patented Feb. 2, 1954 mcmrrro nsnma 'roor. John 1!. Kirby II, Houston, Tex. Application is, so, 1952, Serial No. 301,682

This. invention pertains to tools for removing undesired materials from a well and more particularly to a magnetic toolfor fishing magnetic junk out of a hole in the earth drilledby' the rotary method,. from which hole oil or gas is to be produced. 1

This application is a continuation-in-part of my prior-application Serial Number 239,901, filed August 2, 1951, entitled Well Tool.

It is the principal object of the invention to provide a magnetic fishing tool which will be more efficient in the removal of junk.

A more specific object of the invention is to provide a magnetic fishing tool in which the distribution of the magnetic field is controlled so as to make it more effective for holding magnetic junk.

A- further object of the'invention is to provide a magnetic fishing tool having fluid circulation means for clearing mud and detritus away from the magnetic junk wherein the fluid path is so positioned as to have a more effective field of action.

Still another object of the invention is to provide a magnetic fishing tool having a. rotary shoe a magnetic fishing tool which will more firmly hold the magnetic junk or fish.

Another object of the invention is to provide a magnetic fishing tool capable of holding a larger number of separate fish.

Still another object of the invention isto provide a magnetic fishing tool which will more nearly assure a one hundred percent removal of all the junk.

Another object of the invention is to provide a magnetic fishing tool that is more easily manufactured and repaired and maintained.

Other objects and advantages of the invention will appear from the following description of two preferred embodiments of the invention.

Reference will be made to the accompanying drawings wherein:

Figure 1 is a vertical section through one form of magnetic fishing tool embodying the invention;

' Figure 2 is a vertical section through another so Claims. (01. 294-055) 2 form of magnetic fishing toolembodying the invention;

Figure 3 is a horizontal section taken on the line 3-3 of Figure 2; v

Figure '4 is a horizontal section taken on the line ll of Figure 2.

Referring to Figure 1 there is shown a magnetic fishing tool including. as a core, a permanent bipolar bar. magnet 10 having opposite poles at. its upper and lower ends. The magnet has the shapev of an elongated cylindrical rod and is tapered or beveled slightly at its ends 7 as shown at H, l2. The magnet is made of one of the modern ferromagnetic alloys having a high retentivity and 'field strength. A suitable mag-- netic material may consist of a combination. of

cobalt, aluminum, nickel and iron. such magnets may also include platinum as one of the alloyed materials and are known as platinum magnets. J

The upper beveled end II of, the magnet is received in a correlative recess l3 in a cylindrical head It. The head is provided with a cylindrical fishing neck I! and has a screw, thread It on its upper end adapted to engage a fluid conduit such as a drill pipe, drill collar, or tubing string. The head has a central fluid passage II in its upper portion communicating with a plurality of circumferentiallyspaced apart downwardly diverging fluid passages, two of which are shown at [8 and It. The lower end of the head is provided with a screw thread 20. The head is made of high permeability ferromagnetic material of low retentivity..

A cylindrical tube or sleeve 30 has an internal thread 3| engaged with the thread 20 on the lower end of the head. Tube or sleeve 30 is made of high permeability low retentivity ferromagnetic material and in conjunction with the head which bridges over between and connects the upper ends 7 of the sleeve and magnet conducts the flux from the upper pole of the magnet down to the level of the lower pole of the magnet where there is induced anannular pole disposed around and concentric with the pole at the lower end of the magnet and of opposite polarity. It is thus apparent that the magnet or core, head, and the sleeve 30 form a magnetic path and that a part of said path is a permanent magnet. It is further apparent that there is a magnetic pole at the lower end of the magnet or core and an opposite polarity magnetic pole at the portion of sleeve v3i! which is disposed adjacent to the lower end i of the core, said opposite polarity magnetic pole being disposed around said core pole.

The cross-sectional area of tube. or sleeve 30 is preferably at least equal to that of magnet core 0., Inasmuch as tube or sleeve 30 also forms a housing surrounding and protectin magnet It, the sleeve is preferably made of tough steel. The inner diameter of the sleeve is greater than the outer diameter of the magnet leaving an annular space I: therebetween.

Space 8! provides a region free of ferromagnetic material to prevent short-circuiting of the magnet so as to insure maximum field intensity at the bottom oi the magnet or core and the bottom .of the housing or sleeve which is disposed around the magnet. Space 32 also serves as a fluid passage and the lower ends of the fluid passages in the head open into space 32.

' A disc-shaped pole plate 40 has a recess .4! in its upper face corresponding to and receiving the lower end of the magnet. Plate 40 extends from the lower end of the magnet or core it into contact with tube or sleeve 30. Sleeve 30 also has a screw thread 42 on its lower end and a rotary shoe 3 has an internal thread II which engages thread 42. The rotary shoe is thus attached to the sleeve and extends downwardly from the lower end of the sleeve. An internal shoulder 45 on the rotary shoe engages 'a correlative shoulder 48 on the pole plate whereby, on tightening the rotary shoe, the whole assembly is firmly held together.. course, while the pole plate is shown as being held in the manner just described it is apparent that it could be maintained in contact with sleeve 80 by any suitable means.

Tube or sleeve 30 and rotary shoe 4! may be considered together as being a shell of magnetic Ring II constitutes an extension of the non-ferromagnetic region 01' space 82. It is thus apfluid passages, such as shown at 5! and 52, ex-. tend through the brass ring 50 and communicate with space 32. It may be added that viewed broadly the central magnetic area of the pole plate forms an extension of the core and when the term core is used in the claims hereof without reference to the pole plate it is to be understood that the term "core may include such an extension.

The pole plate partially bridges the gap between the lower ends of the magnet and housing so as to reduce the reluctance of-the magnetic circuit and help maintain the magnetism of the permanent magnet. The gap is sufilcient however to cause the field to be distributed over the inner and lower surfaces of the rotary shoe and its teeth. Due to the concentric disposition of the magnetic circuit, the flux lines are radialand hence more concentrated near the center of the tool. Small pieces of junk will therefore be drawn to the center pole and will not bridge over the gap. Large pieces will bridge only part of the gap in a particular sector of the radial fleld.

posed adjacent to the lower end or the core. The

core, head, and shell form a magnetic path, there being a magnetic pole at the lower end of the core and an opposite polarity magnetic pole at around the core pole.

Therefore, the contacting of even several bit cones and many hearings will not completely short circuit the magnet which will still hold additional junk on contact therewith. It may be noted that although the magnet exerts a strong attraction for junk not in contact with it when brought into proximity therewith, by far all of the junk is drawn by the radial field in- Therotary shoe may have any desired axial I extent and number of teeth and may be of helical shape such as that shown on page 740 of the 1951 edition of the Composite Catalogue of Oil Field and Pipe Line Equipment. The shoe chosen should be adapted to' the particular type and disposition of junk being fished for. I! the junk is fiat on the bottom of the hole, a plain ring having no teeth and coplanar with the pole plate bottom face would be suitable. Where there are a number of drill bit cones to be recovered, a toothed shoe as shown would be suitable. A helical shoe would be useful, in recovering Junk standing on end and leaning against one side of the hole.

Pole plate 4! is a composite member including a central area of disc-shape adjacent the lower end of the magnet core and formed of tough rerromagnetic materialsuch as mild steel. The pole platealso includes an outer ring of magnetic material, the magnetic material being similar to that of the central area. Between the central area and the outer or peripheral area is a ring sures that the junk or fish is cleared of mud and detritus when it is in the position where it is most readily picked up by the magnetic fleld. The circumferential disposition of the fluid es around the central pole insures that the es will not be blocked by the first junk contacted.

, but also to protect the magnet againstdamage during fishing operations, magnets of this type often being somewhat brittle. The three sections of the pole plate should be either cast or soldered together to insure maximum strength.

After the tool has been assembledthe masnetization of the magnet may be. accomplished by placing the whole tool in a strong unidirectional field. On removal of the tool from the field the flux reverses in the housing. By magnetizing the magnet in this manner while assembled in the tool, a much greater fleld strength is obtained than if the magnet is separately energized ,and then assembled in the tool. The magnetic circuit of the'fishing tool comprising the bar magnet together with the highly permeable low retentivmethod lust described.

. i. of brass or other non-ferromagnet c Tl rring now to Figure there is shown a its upper and lower edges. sages such as I29, I80 extend through the sleeve tool generally similar to that shown in Figure}. Only the points of difference needbe described. The magnet I is a frustum of a cone providing a larger cross section at the upper end than at the lower end. This increases the non-ferromoved from the upper ends and. it is desirable to have as low a reluctance path as possible, Also, the larger volume of permanentmagnet material at the upper end provides a maximum magnetizing force in the circuit.

The upper end of the magnet [is provided with a threaded stud IOI engaging a threadedhole I02inhead I03.

Theinner surface of the steam is provided with a plurality of axially extending, circumferentially spaced channels of grooves such as III (see also Figure 3) which form part of the nonferromagnetic region between the magnet and sleeve. -A ring or sleeve II 2 of brass or other non-ferromagnetic material is telescoped within the sleeve I28 in contact with the inner surface thereof. The ring has a larger-inner diameter than the outer diameter of the magnet. The ring or non-magnetic material sleeve II2 thus divides the non-ferromagnetic region between the magnet and the magnetic material sleeve I into an inner annular passage adjacent the magnet and a plurality of outer passages formed by the non-magnetic material sleeve and the .channels in the magnetic material-sleeve. The outer passages are in communication with passage I I3 in the fishing neck by means of the plurality of downwardly diverging circumferentially spaced fluid passages such as H4, H5. The inner passage is in communication with the exterior of the tool through a plurality of upwardly diverging fluidpassages such as H6, H1.

.The lower 'ends of the outer passage are in communication with the bottom face of the tool through a plurality of downwardly converging circumferentially spaced fluid passages such as H9, I20 through the pole plate I2I. The inner passage is in communication with the lower face of the tool through a plurality of circumferentially spaced fluid passages such as I22, I28 through the pole plate which are staggered relative to passages 9, I20. The passages 'II9, I20 and I22, I23 are entirely within the outer ferromagnetic ring I24 of the pole plate which is separated from the central ferromagnetic area I25 by a ring I20 of brass or other non-ferromagnetic material.

Seal rings I04, I05 disposed in channels I08, I01 in the upper and lower ends of sleeve II2,

seal between the upper and lower ends of the sleeve and the head I03 and pole plate I2I respectively. The seal rings prevent leakage across the lower face of the head from passages I II, I I5 topassages H6, H1, and across the upper face of the pole plate which would by-pass passages II9,- I20 and I22, I22.

A packer comprising an expansible sleeve I21 surrounds the sleeve I28 and is sealed thereto at Avplurality of pas- I28 between the interior of the packer and the channels inside the sleeve. r

The tool of Figure 2 is thus arranged for re-- inwardly across the pole plate and back up around the central portion of the pole plate and the permanent magnet and thence out of the tool into the annulus between the drill string and the walls of the well I50. I' 'luid pressure is transmitted to the interior of the packer sleeve and expands it against the well wall to prevent normal circulation. The radially inward direction of the fluid across the pole plate addsto the magnetic force acting in the same direction so as to facilitate the movement of lunk'metal such as bit cones III, I52 and I52, toward the lower end of the magnet.

-It will be apparent that some of the ad .-vantages of the invention couldbe obtained by making the magnetic material sleeve of highly, retentive material and the central bar of low retentivematerial. Also, the head and pole plate might be made of highly retentive material.

Also, both the magnetic material sleeve and central bar could be made of highly retentive material. However, the previously described arrangement is much to be preferred because it facilitates the magnetization of the tool and enables the magnetic material sleeve, head, and pole plate to be made of tough shock and wear resisting material.

While preferred embodiments of the invention have been shown and described, it is obvious that many modifications thereof can be made by one skilled in the art without departing from the spiritof the invention and it is intended to protect by Letters Patent all forms of the invention falling within the scope of the following claims.

I claim: a

1. A magnetic fishing tool comprising an elongated core of magnetic material having an upper end and a lower end, a'tubular shell of magnetic material disposed around said core andspaced therefrom to'provide aispace between said shell and core, saidshell having an upper'end and a portion of said shell being disposed adjacent to.

- of said core and an Opp site polarity magnetic pole at the portion of said shell disposed adjacent to the lower end of said core, said opposite polarity magnetic pole being disposed around said core pole, means to admit fluid to said space between said shell and core, means to conduct lengthwise of said space fluid so admitted, and

meansto discharge from said space fluid so conducted.

'2. A magnetic fishing tool comprising an elongated permanent magnet core having an upper end and a lower end, a tubular shell of magnetic material disposed around said core and spaced therefrom to provide a space-between said shell and core, said shell having an upper end and a portion of said shell being disposed adjacent to the lower end of said core, a head of magnetic material connecting said core and said shell at the upper ends thereof, said core, head, and shell forming a portion of a magnetic path, there being a magnetic pole at the lower encrof said core aeeamv lower end of said core, said opposite polarity magnetic pole being disposed around said core pole, means to admit fluid to, said spacebetween said shell and core, said fluid-admitting meansv opening into-said spade above'the level of the lower end of said core, and means to discharge downwardly from said space and between said opposite polarity poles fluid so admitted.

3. A magnetic fishing tool comprising an elongated cylindrical permanent magnet core having an upper end and a lowerend, a cylindrical shell of magnetic material disposed around said core a portion of said shell being disposed adjacent to density progressing inwardly toward said core pole to urge Junk contacted by said tool inwardly toward said core pole, means to admit fluid to said annular space between said shell and core, and means to discharge downwardly from said annular space fluid so admitted, said fluid dis- 'the lower end of said core, a head of magnetic charge means surrounding said core pole to disgated permanent magnet core having an upper end and a lower end, a tubular sleeve of magnetic material disposed around said core and spaced therefrom to provide a space between said sleeve'and core, said sleeve having an upper end and a lower end, the lower end of said sleeve being located adjacent to the lower end of said core,

a head of magnetic material connecting said core and said sleeve at the upper ends thereof. a plate contacting the lower endof said core and extending from the lower end of said core into contact with said sleeve, said plate including a central area of magnetic material contactirfg the lower end of said'co're and a peripheral area of magnetic material contacting said sleeve, said central plate area, core, head, sleeve, and peripheral plate area forming a portion of a magnetic path, there being a magnetic pole at said central plate area and an opposite polarity magnetic pole at said peripheral plate area disposed around said central area pole, means to admit fluid to said space between said sleeve and core, and means to discharge from said space fluid so admitted.

5. A magnetic flshing tool comprising an elongated cylindrical permanent'magnet core having an upper end and a lower end, a cylindrical sleeve of magnetic material disposed around said core and spaced therefrom in concentric relation thereto to provide an annular space between said sleeve and core, said sleeve having an upper end disposed adjacent to the upper end of said core and a lower end disposed adjacent to the lower end of said core, a head of magnetic material connecting said core and said sleeve at the upper ends thereof, a plate connecting the lower ends ot-said" core and said sleeve, said plate including a central area of magnetic materialcontactinigthe lower end of said core and an outer periphgated cylindrical permanent magnet core having, an upper end and a lower end, a cylindric al,sl i el l ofmagnetic materialdisposediaround said core eral area of magneticmaterial contacting said. sleeve, there being a ring of non-magnetic ma terial disposed between and separating said cen-- tral plate area and said peripheral plate-area,

said central plate area, core, head, sleeve, and

peripheral plate area forming a portion of av magnetic path, there being a magnetic pole at said central plate area and an opposite polarity magnetic pole at said peripheral'plate area disposed aroundsaid central area pole to provide radial magnetic flux lines of increasing density progressing inwardly toward said central area passages opening into said annular space be-.

tween the lower end of said core and said sleeve, and means to admit fluid to said annular space between said sleeve and core.

6. A magnetic fishing tool comprising an elongated permanent magnet core having an upper end and a lower end, a tubular sleeve 01' magnetic material disposed around said core and spaced therefrom to provide a space between said sleeve and core, said sleeve having an upper end and a lower end, a head of magnetic material connecting said cor and said sleeve at the upper ends thereof, a shoe attached to said sleeve and ext'endng downwardly from the lower end of said sleeve, said core, head, sleeve and shoe forming a portion of a magnetic path, there being a magnetic pole at the lower end of said core and an opposite polarity magnetic pole at said shoe disposed around said core pole, means to admit fluid to said space between said sleeve and core, said fluid-admitting means opening into said space above the level of the lower end of said core, and means to discharge downwardly from said space fluid so admitted, saiddfluid discharge means being surrounded by said shoe and being located adjacent to said shoe.

7. A magnetic fishing tool comprising an elongated permanent magnet core having'an upper end and a lower end, a tubular shell of magnetic material disposed around said core and spaced therefrom to provide a space between said shell and core, said shell including a tubular sleeve having an upper end and a lower end and a shoe attached to said sleeve and extending downwardly from the lower end of said sleeve, 8 portion of said shell being disposed adjacent to the lower end of said core, a head of magnetic material connecting said core and said shell at the upper end of said core and at the upper end of said sleeve forming a part of said shell,'a plate including a central area of magnetic material contacting the lower end of said core and a pearea forming a portion of a magnetic path, there being a magnetic pole at said central plate area and an opposite polarity magnetic pole at said peripheral plate area disposed around said central area pole, means to admit fluid to said space between said shell and core, said fluid admitting means opening into said space'above the level of the lower end of said core, and means to discharge downwardly from said space fluid so admitted.

8. A magnetic fishing tool comprising an elonand spaced therefrom in concentric relation thereto to provide aspace between said shell and core, said shell inciuding acylindrical sleeve having an upper end and a lower end and a shoe attached to said sleeve and extending downwardly from the lower end of said sleeve, the lower end of said sleeve being disposed adjacent to the lower end or said core, a head of magnetic material connecting said core and said shell at the upper end of said core and at the upper end of said sleeve forming a part of said shell, a plate connecting the lower ends of said core and said sleeve, said plate including a central'area oi magnetic material contacting the lower end of said core and an outer peripheralv area of magnetic material contacting said sleeve, there being a ring of non-magnetic material disposed between and separating said central plate area and said peripheral plate area, said central plate area, core, head, sleeve, and peripheral plate area forming a portion or amagnetic path, there being a magnetic pole at said central plate area'and an opposite polarity magnetic pol at said peripheral plate area disposed around said central area pole to provide radial magnetic flux lines of increasing density progressing inwardly toward said central area pole, a plurality of fluid passages through said plate circumferentially disposed around the lower end of said core, the upper ends of said passages opening into the space between the lower end of said core and said shell, and means to admit fluid to said space between said shell and core.

9. A magnetic fishing tool comprising an elongated permanent magnet core having an upper end and a lower end, a tubular sleeve of nonmagnetic material disposed around said core, a tubular sleeve of magnetic material disposed around said sleeve of non-magnetic material, said magnetic material sleeve having an upper end and a portion or said magnetic material sleeve being disposed adjacent to the lower end of said core, a head of magnetic material connecting said core and said magnetic material sleeve at the upper ends thereof, said core, head, and magnetic material sleeve forming a portion of a mag netic path, there being a magnetic pole at the lower end oi. said core and an opposite polarity lo material sleeve disposed adjacent to the lower end or said core, said opposite polarity magnetic discharge fluid from said passage at the upperend thereof.

11. A magnetic fishing tool comprising an elongated permanent magnet core having an upper end and a lower end, a-tubular sleeve of nonmagnetic material disposed-around said core, a

tubular sleeve of magnetic, material disposed around said non-magnetic material sleeve, said magnetic material sleeve having an upper end and a lower end, said lower end being disposed adjacent the lower end of said core, a head of magnetic material connecting said core and said magnetic material sleeve at the upper ends thereof, a plate connecting the lower ends of said core and said magnetic material sleeve, said plate including a central area of magnetic material contacting the lower end of said core and an outer peripheral area or magnetic material contacting said magnetic material sleeve, there being a ring of non-magnetic material disposed between and separating said central plat area and said peripheral plate area, said central plate area, core, head, magnetic material sleeve, and peripheral I plate area forming a portion of a magnetic path,

magnetic pole at the portion of said m netic material sleeve disposed adjacent to the lower end oi. said core, said opposite polarity magnetic pole being disposed aroundsaid core pole, a; fluid passagelocated between said magnetic material sleeve and said non-magnetic material sleeve and extending lengthwise'thereof, said fluid passage having an upper end and a lower end, mean to connect the upper end of said fluid passage to a source of fluid, and means to discharge fluid from the lower end otsaid passage adiacent the level of the lower end of said core.

10. A magnetic fishing tool comprising an elongated permanent magnet core having an upper end and a lower end, a tubular-sleeve of nonmagnetic material disposed around said core, a tubular sleeve of magnetic material disposed around said sleeve of non-magnetic material, said magnetic material sleeve having an upper end and a portion of said magnetic material sleeve being disposed adjacent to thelowerend or said core, a head of magnetic material connecting said core and said magnetic material sleeve at.the upper ends thereof, said core, head, and magthere being a magnetic pole at said central plate area and an opposite polarity magnetic pole at said peripheral plate area disposed around said central area pole, a fluid passage located between said magnetic material and non-magnetic material sleeves and extending lengthwise thereof,

said passage having an upper end and a lower end, means to conduct fluid through saidhead to theupper end of said fluid passage, and means to discharge fluid from thelower end of'said passage adjacent the level of the lower end of said core.

12. A magnetic fishing tool comprising an elongated permanent magnet core having an upper end and a lower end, a tubular sleeve oi'nonmagnetic material sleeve having an upper end and a lower end, said lower end being disposed adjacent the lower end of said core, a shoe attached to said magnetic material sleeve and extending downwardly from the lower end of said sleeve, a head of magnetic material connecting said core and said magnetic material sleeve at the upper ends thereof, a plate connecting the netic material sleeve forming a portion of a maglower ends oi said core and said magnetic material sleeve, said plate including a central area of magnetic material contacting the lower end of said core and an outer peripheral area of magnetic material contacting said magnetic material sleeve, there being a ring of non-magnetic material. disposed between and separating said central plate area and said peripheral plate area, said central plate area, core, head, magnetic material sleeve, and peripheral plate area forming a portion of a magneticpath, there being a magnetic pole at said central plate area and an opposite polarity magnetic pole at said peripheral plate area disposed around said central area pole, a fluid passage located between said magnetic material and non-magnetic material sleeves and extending lengthwise thereof, said passage hav- 11 ing an upper end and a lower end, means to conduct fluid through said head to the upper end of said fluid passage, and means to discharge fluid from the lower end of said passage adjacent the level of the lower end of said core.

13. A magnetic flshing tool according to claim 11 including a fluid passage between said core and said nno-magnetic material'sleeve, means to conduct fluid discharged from the lower end of the flrst said passage to the lower end of the last passage, and means to discharge fluid from the upper end of the last said passage to the exterior or the tool.

14. A magnetic fishing tool according to claim 11 in which said fluid discharge means includes a group of passages through said peripheral plate area annularly disposed around said core.

15. A magnetic fishing tool according to claim 14 including a. second group of fluid passages through said plate annularly disposed around said core and disposed radially inwardly from the flrst said group of epassages, a fluid passage betweensaid core and said non-magnetic material sleeve in communication at its lower end with said second group of-passages, and means at the upper end of the last passage to place it in communication with the exterior of the tool.

16. A magnetic fishing tool comprising an elongated permanent magnet core having an upper end and a lower end, a tubular sleeve of magaeeaovv said second passage at the lower end thereof, and.

means todischarge fluid from said second passage at theupper end thereof.

18. A magnetic fishing tool comprising an elongated permanent magnet core having d'n upper end and a lower end, a tubular sleeve of.

non-magnetic material disposed around said core, a tubular sleeve of magnetic material disposed around said sleeve' of non-magnetic materlal, said magnetic material sleeve being disposed adiacent to the lower end of said core, a head of magnetic material connecting said core and said magnetic material sleeve at the upper ends thereof, said core, head and magnetic material sleeve forming a portion of a magnetic path.

' there being a magnetic pole at the lower end of said core and an opposite polarity magnetic pole at the portion of said magnetic material sleeve disposed adjacent to the lower end of said core,

I said opposite polarity magnetic pole being disneticmaterial disposed around said core, a

tubular sleeve of nonmagnetic material disposed between and separating said core and said sleeve 'of magnetic material, said sleeve of magnetic material having an upper and disposed adjacent the upper end or said core and a lower end disposed adjacent tothe lower end of said core, a bridge of magnetic material extending over the top of said non-magnetic material sleeve and connect: ing said core and said magnetic material sleeve at the upper ends thereof, said. core, bridge, and magnetic material sleeve forming a portion or a magnetic path, there being a magnetic pole atthe lower end of said core and an opposite polarity magnetic pole at the portion of said magnetic material sleeve disposed adjacent to the lower end of said core, said opposite polarity magnetic pole being disposed around said core pole, means to connect said tool to a source of fluid, means to discharge fluid from said tool near the level of l the lower end of said core, and means forming an posed around said core pole, a fluid passage located between said magnetic material sleeve and said non-magnetic material sleeve and extending lengthwise thereof, means to connect the upper end of said fluid passage to a source or fluid, means to discharge fluid from said passage adja-' cent the level of the lower end of said core. a sec ond fluid passage located between said nonmagnetic material sleeve and said core and extending lengthwise thereof, said secondfluid passage having an upper end and a lower end, means to admit fluid to said second passage at the lower end thereof, means to discharge fluid from said second passage at the upper end thereof, and an rial, said magnetic materialsleeve being disposed adiacent to the lower end of said core, a head .of

magnetic material connectingsaid core and said magnetic material sleeve at the upper ends thereof, said core, head and magnetic material sleeve forming a portion of a magnetic path, there being a magnetic pole at the lower end of said core and an opposite polarity magnetic pole at the portion of said magnetic material sleeve disposed adjacent to the lower end of said core, said opposite polarity magnetic pole being disposed around said core pole, a fluid passage located between said magnetic material sleeve and said non-magnetic expansible sleeve surrounding said magnetic material sleeve, said expansible sleeve having upper and lower edges and being sealed to said magnetic material sleeve at said upper and lower edges, and means extending through said magnetic materialsleeve to admit fluid under pressure to the interior of said sleeve to expand said sleeve against the inside of a well in which said tool is placed to prevent flow of fluid outside the tool lengthwise past said expansible sleeve.

19. A magnetic fishing tool comprising an elongated permanent magnet core having an upper end and a lower end, a tubular sleeve of nonmagnetic material disposed around said core, a tubular sleeve of magnetic material disposed around said sleeve of non-magnetic material, the inside diameter of the magnetic material sleeve being equal to'the outside diameter of the nonmagnetic material sleeve whereby the said sleeves are in engagement one within the other, said magnetic material sleeve having an upper end and a portion 01' said magnetic material sleeve being disposed adjacent to the lower end of said core, a head of magnetic material connecting said core and said magnetic material sleeve at the upper ends thereof, said core, head and magnetic material sleeve forming a portion of a magnetic path, ther being a'magnetic pole at the lower end of said core andan opposite polarity magnetic pole at the portion or said magnetic material sleeve disposed adiacent to the lower end of said core, said opposite polarity magnetic pole material sleeve and extending lengthwise theredisposed around n core pole a mummy of fluid passages located between said magnetic material sleeve and said non-magnetic material sleeve formed by grooves in one of said sleeves and extending lengthwise thereof, each of said fluid passages having an upper end and a lower 1 end, another fluid passage located :between said non-magnetic material sleeve and said core and extending lengthwise thereof, said other fluid passage also having an upper end and a lower end, means to connect said head to a fluid-conducting pipe, means to conduct fluid through said head to the upper ends of the fluid passages located between said magnetic material and nonsaid sleeve at the upper ends thereof, means including a connector rising from the upper end of said head for connecting said fishing tool to means for raising or lowering the tool in awell,

'and means to provide protection for the core of tough magnetic material in contact with the magnetic material sleeves, means to discharge fluid from the lower ends of the passagesbetween said magnetic material and non-magnetic material sleeves toward thelower-end of the passage between said non-magnetic material sleeve and said core, and means to discharge fluid from the upper end of said last named passage to the exterior of said tool.

20. A magnetic fishing tool comprising an elongated permanentmagnet core having an upper end and a lower end, a tubular sleeve of magnetic material disposed around said core and spaced therefrom, said sleeve having an upper end and a lower end, the lower end of said sleeve being located adjacent to the lower end of said core, the cross-sectional area of said' core in a plane substantially at right-angles to the longitudinal axis of said core being substantially uniform throughout the length of said core, the

cross-sectional area of said sleeve in a plane substantially at right-angles to the longitudinal axis of said sleeve being substantially uniform throughout the length of said sleeve and being substantially equal to said cross-sectional area of 'said core, a head of magnetic material connecting said core and said sleeve at the upper ends thereof, means including a connector rising from the upper end of said head for connecting said fishing tool to means for raising or lowering the tool in a well, and means to provide protection for the core against damage by mechanical shock when the tool strikes a .hard object such as a piece of junk in a well bottom, said protecting means including a plate of'tough material covering the lower end of said permanent magnet core, non-magnetic means disposed adjacent the lower end of said core and magnetically separating said sleeve from said core, and means supporting the outer edge of said plate from the lower end of said sleeve, said protecting means bridging the lower end of said space between said sleeve and core, said plate having at least a central portion of magnetic material in contact with the lower end of'said core and formingv an extension thereof, said core, head and sleeve forming a portion of a magnetic path, there being a magnetic pole at the lower end of said core and an opposite polarity magnetic pole at the lower end of said sleeve located adjacent to the lower end of said core, said opposite polarity magnetic pole being disposed around said core pole.

21. A magnetic fishing tool comprising an elongated cylindrical permanent magnet core having an upper end and a lower end, a cylindrical sleeve of magnetic material disposed around said core and spaced therefrom in-concentric relation thereto to provide an annular space between said sleeve and core, said sleeve having an upper end disposed adjacent to the 'upper end of said core and a lower end disposed adjacent to the lower end of said core,-' a head of magnetic material connecting said core and lower end of said core and forming ansexten- .slonthereof, an annular ring of non-magnetic ing said disc at the outer periphery thereof, and

means supporting the outer edge of said ring from the lower end of said sleeve, said core, head and sleeve forming a portion of a magnetic path, there being a magnetic pole at the lower end of said core and an opposite polarity pole at the lower end of said sleeve surrounding said core pole to provide radial magnetic flux lines of increasing density progressing inwardly 'toward said core pole, said annular ring'of non-magnetic material being located between said opposite polarity magnetic poles and separating the-lower end of said core and the lower end of said sleeve.

22. A magnetic flshing tool comprising an elongated cylindrical permanent magnet core having an upper end and a lower end, a cylindrical leeve of magnetic material disposed around said core and' spaced therefrom in concentric relation thereto to provide an annular space between said sleeve and core, said sleeve having an upper end disposed adjacent to the upper end of said core and a lower end disposed adjacent to the lower necting said core and said sleeve at the upper ends thereof, said core, head and sleeve forming a portion of a magnetic path, there being a magnetic pole at the lower end of said core and an opposite polarity magnetic pole at the lower end of said sleeve disposed adjacent to the lower end of said core, said opposite polarity magnetic pole being disposed around said .core pole to provide radial magnetic flux lines of increasing density progressing inwardly toward said core pole to urge junk contacted by said tool inwardly toward said core pole, means to admit fluid tosaid space between said sleeve and core, and a plurality of fluid-discharge ports surrounding said core pole, said fluid-discharge ports being located between the lower end of said core and the lower end of said sleeve to'discharge fluid from said ports against junk tending to bridge said opposite-polarity poles and therefore assist in having junk concentrate on said core pole.

23. A magnetic fishing. tool comprising an elongated cylindrical permanent magn t core having an upper end and a lower end, a ylindrical sleeve of magnetic material disposed around said core and spaced therefrom in concentric relation thereto to provide an annular space between said core and sleeve, said sleeve having an upper end disposed adjacent to the upper end of said core and a lower end disposed adjacent to the lower end of said core,a head of magnetic material connecting said core and said sleeve' at the upper ends thereof, a plate connecting the lower ends of said core and saidsleeve, said plate including a central area of magnetic material contacting the lower'end of said core, and-an outer peripheral area of magnetic materialccintacting said sleeve, said central area projecting said peripheral areaproiecting radially inwardly oi. the lower end of said sleeve, there being a ring oi non-magnetic material disposed between and separating said central plate area and said peripheral platearea, said-central plate area, core, head, sleeve and peripheral plate area forming a portion 01 a magnetic path, there being a magnetic pole at said'central plate area and an opposite polarity'magnetic pole at said peripheral plate area disposed around said central area pole to provide radial magnetic flux lines of increasing density progressing inwardly toward said central area pole to urge Junk contacted by said tool inwardly toward said central area pole, and a plurality of passages through said plate circumi'erentially disposed around the lower end 01' said core, the upper ends of said passages opening into the space between the lower end of said core and said sleeve.

24. A magnetic flshing tool comprising a single elongated cylindrical permanent magnet core having an upper end and a lower end, a cylindrical sleeve 01 magnetic material disposed around said core and spaced therefrom in concentric relation thereto to provide an annular space between said sleeve and core, said space between said core and said sleeve being devoid oi magnetic material. said sleeve having an upper end disposed adjacent to the upper end of said core and a lower end disposed adjacent to the lower end of said core, a head oi-magnetic material connecting said core and said sleeve at the upper ends thereof, a plate of tough material covering the lower end of said-permanent magnet core to provide protection-for the core against mechanical injury, said plate bridging the lower end of said space between said sleeve and core, means supporting the outer edge of said plate from the lower end of said sleeve, said plate having a central portion of magnetic material in contact with the lower end of said core forming an extension thereof, said core, head and sleeve forming a portion oi a magnetic path, there being a magnetic pole at the lower end of said core and an opposite magnetic pole at the lower end of said sleeve surrounding said core pole to provide radial magnetic flux lines 01- increasing density progressing inwardly toward said corepole, said plate including an annular ring of non-magnetic material located between said opposite polarity magnetic poles and separating the lower end of said core and the lower end of said sleeve, said head having a recess in its lower side correlative to and receiving the upper end of said permanent magnet core, said plate having a recess in its upper side correlative to and receiving the lower end of said permanent magnet core, said core being held centrally in said sleeve by said head and plate 25. A magnetic fishing tool comprising an elongated permanent magnet core having an upper end and a lower end, a tubular shell oi magnetic material disposed around said core and spaced therefrom to provide a space between said shell and core, "said shell having an upper end and a portion of said shell being disposed adjacent to the lower end of said core, a head of magnetic material connecting said core and shell at the upper ends thereof, said core, head, and shell forming a portion of a magnetic path, there being a magnetic pole at the lower end 01' said core and an opposite polarity magnetic pole at the portion or saidshell disposedadiaoent to the lower end or said core, said opposite polarity magnetic pole being disposed around said core pole, a pipe connected to the upper side or said head, means on said pipe to connect it to a fluid conduit, a plurality of fluid passages through said headconnecting the interior of said pipe with the upper end or said space between said shell and core, said passages being disposed around the axis'or said tool, said pipe and passages and said space between said shell and core providingmeans to conduct downwardly fluid admitted from a fluid conduit connected to said pipe and to discharge downwardly from said space between said opposite polarity poles fluid so admitted.

26. A magnetic fishing tool comprising an elongated permanent magnet core having an upper end and a lower end, a tubular shell of magnetic material disposed around. said core and spaced therefrom to provide a space between said shell and core, said shell having an upper end and a portion of said shell being disposed adjacent to the lower end of said core, a head of magnetic material connecting said core and said shell at the-upper ends thereof, means to provide protection ior'the core against mechanical inJury, said protecting means including a plate of tough material covering the lower end of said permanent magnet core, non-magneticmeans disposed adjacent the lower end or said core and magnetically separating said shell from said core, and means supporting the outer edge oi. said plate from the lower end or said shell, said protecting means bridging the lower end of said space between said shell and core, said plate having at least a central portion or magnetic material in contact with the lower end oi! said core iorming an extension thereof, said core,

head, and shell forming a portion of a magnetic path, there being a magnetic pole at the lower end of said core and an opposite polarity magnetic pole at the portion of said shell disposed adjacent to the lower end of said core, said opposite polarity pole being disposed around said core pole, a pipe connected to the upper side of said head, means on said pipe for connecting it to a fluid conduit, a plurality of passages through said head connecting the interior of said pipe with the upper end of said space between said core and said shell, said passages being disposed around the axis 01' said tool, a plurality of ports through said plate connecting the lower end of said space with the exterior oi said tool at the lower end thereof, said pipe and passages providing means to admit fluid to the upper end of said space irom'a conduit connected to said pipe, said ports providing nozzle means to Jet discharge downwardly from said space and between said opposite polarity poles fluid so admitted, and said space formed between said core and shell providing a fluid channel to conduct fluid down through said tool from said pipe and a portion or said shell being disposed adjacent to the lower end of said core, a head of magnetic material connecting said core and said shell at the upper ends thereof, a plate of tough material covering the lower end or said permanent magnet core to provide protection for the core against mechanical iniury, said plate bridging nulsr portion of aesaow 17 the lower end of said space between said shell and core, means supporting the outer edge of said plate from the lower end of said shell, said plate having a central portion of magnetic material in contact with the lower end of said core forming an extension thereof and an annular portion of non-magnetic material surrounding said central portion of magnetic material and separating said central portion from said shell, said core, head, and shell forming a portion of a magnetic path, there being a magnetic pole at the lower end of said core and an opposite polarity magnetic pole at the portion of said shell disposed adjacent to the lower end of said core, said opposite polarity pole being disposed around said core pole, a pipe connected to the upper side of said head, means on said pipe for connecting it to a fluid conduit, a plurality of passages through said head connecting the interior of said pipe with the upper end of said space between said core and said shell, said passages being disposed around the axis of said tool, a plurality of ports through said plate connecting the lower end of said space with the exterior of-said tool at the lower end thereof, said p pe and passages providing means to admit fluid to the upper end of said space from a conduit connected to said pipe, said ports providing nozzle means to jet discharge downwardly from said space and between said opposite polarity poles fluid so admitted, and-said space formed between said core and shell providing a fluid channel to conduct fluid down through said tool from said pipe and passages to said ports, said head having a recess in its lower side correlative to and receiving the upper end of said permanent magnet core, said plate having a recess in its upper .side correlative to and receiving the lower end of said permanent magnet core, said core being held centrally in said tool between said head and plate, and sa d shell holding said head and Plate together.

28. A magnetic fishing tool comprising an elongated permanent magnet core having an upper end and a lower end, a tubular sleeve of magnetic material disposed around said core and spaced therefrom to provide a space between said sleeve and core. said sleeve having an upp r end and a portion of said sleeve being dis- DOsed adjaoent to the lower end of said core, a head of magnetic material connecting said core and said sleeve at the upper ends thereof, a plate of tough material covering the lower end of said permanent magnet core to provide protection for the core against mechanical injury, said plate bridging the lower end of said space between said sleeve and core, a shoe having an annular upper end screwed to the lower end of said sleeve and having an inwardly extending shoulder extending beneath the outer edge oi said plate, said plate having a central portion of magnetic material in contact with the lower end of said core forming an extension thereof and an annon-magnetic material surrounding said central-portion of magnetic material and separating said central portion from said sleeve, said core. head, and sleeve forming a portion of a magnetic path, there being a magnetic pole at the lower end of said core and an opposite polarity magnetic pole at the portion of said sl posed adjacent to the lower end can of said on said pposite polarity pole he s I and said exterior surface ing vertically upward from the upper part of said head and integral therewith, said pipe having a'screw thread formed at its upper end for connecting it to a fluid conduit, a plurality of passages through said head connecting the in-. terior of said pipe with the upper end of said space between said core and said sleeve, said passages terminating at their lower ends between said core and sleeve at diflerent azimuthal positions around the axis of said core, a plurality of ports through said plate connecting the lower end of said space with the exterior of said tool at the lower end thereof, said pipe and passages providing means 'to admit fluid to the upper end of said space from a conduit connected to said pipe, said ports providing nozzle means to jet discharge downwardly from said space and between said opposite polarity poles fluid s0 admitted, and said space formed between said core and sleeve providing a' fluid channel to conduct fluid down through said tool from said pipe and passages to said ports, said head having a recess in its lower side correlative to andreceiving the upper end of saidpermanent magnet core, said plate having a recess in its upper side correlative to and receiving the lower end of said permanent magnet core, said core being held centrally in said tool between said head and plate, and said sleeve holding said head and plate together.

29. A magnetic fishing tool comprising a permanent magnet core having an upper end and a lower end, a sleeve of magnetic material disposed around said core and spaced therefrom, said sleeve having an upper end and a lower end, theilower end of said sleeve being located adjacent to the lower. end of said core, a head of magnetic material connecting said core and sleeve at the upper ends thereof, said core, head and sleeve forming a portion of a magnetic path, there being a magnetic pole at the lower end of said core and an opposite polarity pole at the lower end of said sleeve surrounding said core pole to provide radial magnetic flux lines of increasing density progressing inwardly toward said core' pole, means supporting said core extending between said core and sleeve, said supporting means providing support for said core adjacent the lower end of said core and including non-magnetic means magnetically separating said core and sleeve, and means fluid through said tool to discharge said fluid downwardly at the lower end of said tool.

30. A magnetic fishing tool according to claim 29 wherein said sleeve has an exterior surface is an exterior surface of said tool and wherein said means to convey fluid through said tool to discharge said fluid discharges said fluid at the lower face of said tool within an area bounded by the inner periphery of said sleeve.

JOHN H. KIRBY, II.

Cited in iii-e file of this patent to convey, 

